This application relates generally to email services. More particularly, the disclosure provided herein relates to systems and methods for mitigating email spam attacks.
Unsolicited bulk email (“UBE,” hereinafter referred to as “spam”) is generally defined as unwanted and/or unsolicited e-mail. Each day, email user accounts controlled by spammers connect or attempt to connect to Internet Service Providers (“ISPs”) to transmit spam. These email user accounts may reside on the same ISP domain to which the spammers connect, or they may reside on other ISPs, corporate mail systems, hosting services, and/or network client mail systems.
It is common for large ISPs to receive hundreds of millions of spam messages each day. The spam messages may be transmitted from millions of email user accounts, some of which may have never before connected to the ISP. Over the last several years, a growing portion of the spam that is sent by spammers is passing through the ISPs' defenses and being delivered into users' mailboxes. At the same time, a growing portion of spam originates from legitimate user accounts associated with ISPs.
Spammers are continuously compromising user PCs and/or email accounts, or creating new email accounts on ISPs. From these accounts the spammers send large volumes of spam messages through the ISP to attack other ISPs. Spammers assume that destination ISPs will not block the traffic from other well-known ISPs. For example, the spammers assume that the destination ISP will not put the ISP's IP address on a blacklist because legitimate users of the ISP would also be blocked as a result. Additionally, spammers send spam from their ISP email accounts to other user accounts on the same ISP. Spammers know that ISPs will not block the ISP's dynamic IP addresses because of the support costs that would result when the blocked dynamic IP addresses are assigned to other users. As a result, ISPs' defense against spam coming from these sources may be limited to spam content filtering.
As a result of being unsure of the sender's identity, lack of reputation, the ever increasing difficulty with ascertaining whether a message is spam, the increasing effectiveness of spammers, the reluctance of ISPs to block other ISPs or client IP addresses associated with the ISPs, and/or other factors, ISPs have an increasingly difficult time improving the effectiveness of current spam blocking and filtering processes. As such, spam is increasingly delivered to ISP members' mailboxes and continues to adversely affected members' experiences using email. In addition, spamming continues to increase ISPs' costs for providing email services.